Vitrified diamond grinding wheel



- Aug. 29, 1944. R. H. LOMBARD 2,356,937

VIlTRIFIE-D DIAMOND GRINDING WHEEL Filed May l0, 1941 2] 10 I3 150 2 l Il 150 I3 I0V Il g g 2, l\1 21' Ha' H94 ROBERT H. LDA/:BARE

lmentioned object.

Patented Aug. 29., 1944 Tammo-marroni 'Gambino man Robert H. Lombard, Worcester, Mass., assigner to Norton Company, Worcester, Mass., a corporation of Massachusetts cuestion May 1o, 194i, sei-iai No. 392,829

9 claims.V (c1. :s1-sor) The invention relates to vitried diamond grinding wheels.

One object of the invention isto provide im proved structures fooivitried bonded diamond grinding wheels and sticks or hones which shall be simple to produce, reliably controllable in processing so as to achieve uniformity of structures in quantity production1 and give consistently good resultsl structural and functional. Another object ofthe invention is to provide a structure for two-part vitrined diamond grinding wheels having an abrasive rim or periphery of a peripheral after pressing of the center, after inversion, after the mold ring has been removed and a twodiameter mold band placed outside of the largest c -mcld plate; 1

and a non-abrasive center, which structure shall be integral and can be "duplicated, with few. if any, rejections during manufacture. Another object of the invention is to provide abrasive articles of the above-mentioned kind withv highly advantageous mechanical or physical'structural elements internally and at the same time, during firing, to control and prevent swelling of either the center or the abrasive portion of a vitriiied bonded diamond grinding wheel. Another'ob- .lect is to provide body materials to take part in building up, during firing, a compound framework usable either in'the abrasive portion to pro# vide improved support i'orv the abrasive grains or in the backing or center for the abrasive portionto provide improved supportfor the latter, Y

and capable ofuse in both the abrasive portion o r in the backing or center, and in any such case to achieve the desired strength of structure while adequately accounting for the veifects of thermal abrasive center. abrasive wheel has certain free-cutting and changes, during manufactura or during use.

withinv the article. Another object is to provide body materials well adapted for conjoint use and coaction in the carrying outv of this last-rH Another object of the invention is to provide a wheel capablev ot mix for a -center for such a being matured into astrong and uniform center in a vitrifying process.v

Other obiects will be in pointed out hereinafter. The invention accordingly consists'in the feapart obvious or in part ',tures'of construction, combinations of elements,

arrangements of parts, and in thesever-al steps and relation and order of each oi said steps to oner or more of the others thereof, all as will be illustratively described herein, and the scopel of the" application of which will be indicated in the following claims.

In vthe accompanying drawing illustrating one Figure 4 shows the mold in the same condition as in Figure 3 afterthe annular space has been illled with diamond ceramic material and the ring reinserted; and

Figure 5 shows the mold of Figure 4 after it is closed. Y

The drawing illustrates the manufacture of a peripheral wheel. From this it shouldnot be understood that peripheral Wheels are more important or manufactured in greater quantities than cup wheels and othershaving an annular plane abrasive surface because perhaps the reverse is the fact, 'but the manufacture of a peripheral ceramic diamond grinding wheel presents particular problems and from the following disclosure the manufacture of a diamond ceramic cup wheel will .be readily understood.

to the great cost of diamonds, it is quite usual to make diamond grinding wheels inthe form oi a thin annulus of diamond abr ve with anon- A ceramic nded diamond wear resisting .properties whichj make it highly desirable for 'certain` grinding operations; It is desirable to make a vitriiied center for such diamond grinding vwheels and in order to make an integral body free fromcracks or strains, it is desirable, to vitrify ther center .or back same time that the rim'lis vitriiled. Swelling is a particular problem and, therefore, it is important to provide a mix both "for atthe the center and the snn'ulus which will not swell during tiring. To prevent the development of strains or cracks in the product. it is important of many possible embodiments of the mechanical features of this invention,v Figure 1 is a cross sectional view of a mold having just been filled with a vitriilable noncentral noie n in uipiste u. plate Il uponthe plate l and that the annulus and thecenter beccnsolidated into a single piece ofuniform density. I shall iirst describe the steps inthe molding technique forthe productionoi' a Vgreen body ready for ilring in a suitable furnace. l s Referring now to Figure l, I provide a large .-ilat plate I and of mold consisting of a plate Il,

a ring Il', andan arbor I2. The ring il just tits plate Il and the arbor I2 Just ts in a I nrst place the at opposite sides of the plate III I position a pair of spacingvblocks I4. I then place the ring II around the plate I and upon the blocks Il, as shown. I then insert the arbor I2 part way into the hole I3. I

now flll the mold with a center non-abrasive mix I5 and level it ofi in a well known manner.

I now transfer the illled mold of Figure 1 on the plate 9 to the bottom plate of a hydraulic press. Referring to Figure 2, I' now place upon t the arbor I2 a plate I6 havingan arbor hole I1 l0 and having a diameter somewhat greater than that of the plate III. I now remove the blocks I4 and temporarily hold up the ring II with my y ilngers. Then I apply the pressure of the hy-l draulic press to the extent of about 250 pounds per square inch. After the ring II starts to move, sufficient grit moves between it and the plate I 0 to prevent the ring II from dropping.

I now strip the mold ring II and invert the mold, locating the plate I6 on the bottom plate of 20 the hydraulic' press. A consolidated center mix I5a is now located between the plates I0 and I6. Then I place a heavy mold band I8 around the plate I6 and upon spacing blocks I9. The mold band I8 has a small inside diameter approxi- 25 mately the same as that of the outside diameter of the plate I6 so as to t upon it with a sliding fit. It has a larger inside diameter separated therefrom by a shoulder 2I. When the band I8 t is raised by the blocks I9, the shoulder` 2| is 30 somewhere between the top and bottom of the plate I0. t

This leaves a space 22 bounded on the bottom by the plate I6, on the outside by the mold band I8, and on the inside by the periphery of the plate I0 and the periphery of the consolidated center I5a. The top of this space 22 to be lled is somewhat below the level of the shoulder 2l. v

Referring to Figure 4, I now fill this space with a diamond containing ceramic mix 23. I then place thering II inside the mold band I8 upon the shoulder 2|, as shown. It will be noted that 'the height of the ring II is the same as that of the plate I0 but the distance from the shoulder 2| to the top of the mold band I8 is slightly less. 45

I now remove the spacing blocks I9 and close the mold to the position shown in Figure 5.r The quantity of material I5 and 23, respectively, is selected so that the two parts of the wheel will or packings of their constituents, and usually so that the two parts of the wheel will have similar densities of packing, that is, the porosity of the rim and the center will be similar. The closing of the mold to the position shown in Figure 5,

' this connection fairly fine grit sizes seem to be,

' be pressed to definite, predetermined densities 50 dated into an integral article which can be reado0 ily handled even before it is red. Such an arti,

cleis termed a.green" wheel in the abrasive industry. l I now strip the mold band I8, remove the plug I2, and then pick oil the plate Il and the plate I 0 and ring. I I. I now have a green'i'wheel c onsisting of a non-abrasive center part I 5b and an abrasive periphery 23a in an integral piece, with ceramic material throughout capable of being fired in a suitable furnace into an integral nonswelled grinding wheel. Y

Considering now the materials which I use to form or ba g lib, the former 'contains vdiamond's while the abrasive periphery 23W and the center ceramic materials, and in accordance with the present invention one or both of the parts contains silicon, or silicon alloy, such as ferro-silicon or aluminum-silicon, all of which are generically referred to herein as metallic silicon, or sometimes las oxidizable metallic silicon. The use of silicon, in -accordance with the manner in which I employ it, has at least two desirable functions: (l) It functions during firing to prevent detrimental swelling of the abrasive body dueto the evolution of certain gases from the material during the burn in a non-oxidizing atmosphere, and (2) since I insure its presenceas granular silicon in the flnal fired article, I cause the silicon to provide at the same time suitable solid granular material for that strongly vitriiied bonded framework of the abrasive body which is essential to the achievement of certain practical advantages such as mechanically strong and adequate support of the diamond grains and consquent low wear during grinding. ,This usey and functuring of silicon has enabled me to make non-swelled diamond containing abrasive bodies of excellent quality bonded with a vitriiled bond matured in the vicinity of l000 C. or below in a non-oxidizing atmosphere.

Silicon of various grit sizes may be used. For example, a grit size may be chosen which con fers the greatest bonded strength on the diamond grains in the abrasive body or wheel. In

more eiective. I have used silicon of grit alle through 100 mesh screen onto 210 mesh screen: silicon which has passed 210V mesh screen; and ball-milled silicon which is the finest of these grit sizes. C

n Examples ci' the calculated compositions for the abrasive periphery involving the use of silicon are:

Example l Example 2 Vol. l Vol. ,L Diamond, 100 grit size 25 25 Silicon, through 100 onto 210 A.-. 25 Silicon, through 210 2i Bond A 35 I5 ores i5 ll -RondAconsistsoi25partsofballclay,2pm-tl' of aluminum powder, and 'I5 parts oi a frit according to the following formula, all parts being by weight:

Parts Borax4 321 Bm'ic arid 25.4 Silica 37.6 Hydrate of alumiml 1.0 Whiting 3.8

'I'he calculated chemical composition of this frit is as follows:

Puel' m2o '1.a cao s. Aho: f i .s- Bios 36.4 sioif o,im

'I'hese wheels were burned at 950 C. for four and body. it should be present'atleast in a proportion great enough to control the swelling which latter does not: both parts lude might otherwise occur during the'burn in a nonform the body material SUDDOIRE Center.

' satisfactorily, and at oxidizing atmosphere. The materials which constitute the remainder of the granular body material should have no harmful eect on the/intended diamond abrasive body; they should not be deleteriously affected by the bond or the burning conditions; they should have no deleterious effect on the diamond abrasive; tribute satisfactorily to the bonded strength oi' the diamond abrasive body, and they should have a coefficient of thermal expansion which causes neither deleterious cracking of the vitried bond nor undesirable stresses in the abrasive body. For example, I have used vitreous silicaAV as sucl substance mixed with silicon to of vitriiied bonded diamond abrasive bodies, and examples of such compositions are given below.l

The above use of. silicon as abody materiall in a diamond containing abrasive bodyburned in a non-oxidizing atmosphere is to be considered as a specific application of a general principle, namely, the use as, body material in a vitrihed bonded, diamond containing abrasive body of a substance or substances which (l) by virtue of their reducing nature or vother properties are capable of preventing or controlling the swell ing caused by gas evolution from the materials during a burn in a non-oxidizing atmosphere. (2) are proportioned in-an amount at least great enough to prevent or control such swelling, and (3) in addition to their qualities ofpreventing swelling are also present in form and amount to be capable of forming, in whole or in part, the granular material `of a vitried bonded iframeworlr' which adords a vsuitable strong, wear-resistant support to the diamond grains of the diamend abrasive/body. Other illustrative substances which may be used for this purpose are ferro-silicon and silicon-aluminum alloys.

My invention further involves the use of granular silicon as a solid constituent or body material of a vitrified bonded body, such as the center lh integrally support for a vitried ing abrasive body, tta of a vitrified wheel. A

A. central supporting center made solely oi granulan vitreoussilica, bonded by a. vitreous bond such as bond A is apt to swell objectionably Lwhen burned inanon-oxidizingeatmosphere due Vto the evolution of gas from its 'constituent materials. This swelling may serlousiydisturb thestructure of portions of the peripheral diamond containing rim which are adjacent to the The use of two parts ol' aluminum powder in the bond diminishes this swelling; but not always suiliciently.. I hve found that the use of granular silicon as the whole or part of the granular constituents of the central supporting disk or backing obviates this swelling the-same time the silicon material for the vitriiied of the supporting center. diamond containing' rim, the the dual function ofxc'onin a non-oxidizing atmosphare and of ,serving as a structural element of the center in that, as in the abrasive-containing rim, the silicon is present in the final or red product, exclusive -of any oxidation product -iformed by part'or some f-it during firing in the process ci controlling swelling, in the form oi' individual grain-like entities or metallic granbonded diamond containsuch as the peripheral rim provides a suitable bonded framework .ll-lere also, as in the silicon grain serves trolling the swelling bonded to and usedas al now-vitrined bond to form a structural part of a compound framework. In the sense that someof the initiauy present metauic silicon is oxidized they should conmaximum bonding support finished sides by Athe bonded diamond grinding center or back mules distributed throughout and bonded by the Ys.

-to be casi mesh onto,2l0 mesh screen cracks to form in the bond glass as a during ring to prevent swelling and hence produces some oxidation product, it' may be said that' the silicon presentin the final vitriiled article to take part in forming this compound framework is preponderantly metallic silicon or silicon per se to distinguish it from any such oxidation product which, in contrast, goes into solution in the molten bond glass during ring. Again, silicon is to be considered only as a speciiic example of substances which make possible attaining the above effects. i

'The principles governing the range of grit sizes of the granular material for the vitrified bonded supporting Vcenter are diierent from those for the diamond containing abrasive body. For the supporting center there is no need to select the grit size with a view to contributing to the diamond abragrit size. As far as sufiicient to provide sive 'grains of a particular strength is concerned it is a supporting centerwhich chanical stresses of the grinding operation without danger of breakage and yet besoft enough futrued. Very fine grit material, such as has been `favors shrinkage during the burning. However,

fairly line material, for example, through 1GB is desirable in the supporting center because it will nullify a tendency. present with coarse grained material, for 1 result of differential expansion between vitriiied bond and the grains of the `body material. Relatively fine grit materialalso. makes it easier to produce well process of. siding by grinding.

Mixtures ci silicon with other suitable solid terial for the vitried bonded supporting center. I have used vitreous silica for such admixed material. In any eventthe material of the supporting center should be so chosen and proportioned that a difference in thermal expansion between the center and the peripheral diamond containing abrasive rim does not cause cracking or breaking of the rim or center. Also, the expansion of the body materials should match that o! the; bond suiiiciently well to prevent cracking of the bond. f

The vitrlile'd ceramic bond of the supporting can to advantage be of a less strongly bonding type than the vitried bond in the" 'diamond abrasive; portion of the wheel or implement. Alsofthe percentage by volume of bond in the center or back can to advantage be less than iii-,the diamond abrasive portion.- It the strong bond and the high volume percentage of bond oi' the diamond abrasive portion is used in the non-abrasive center or back, the latter will be so hard that it will beunnecessarily diiicult to true it, and there will be danger of breakingthe product during truing. Therefore, I use a weaker bond /inr the non-abrasive center-@or back, for example, one which contains more clay; and I decrease the volume percentage of bond .in

ythe ,center in relation to that in the diamond The weaker bonding of the i will endure the mef ball milled finer than 210 grit size, is lusually to be avoided in the supporting centers ing during truing but, of course, the product retains adequate mechanical strength for the grinding operation. The above features of weakened bond composition and lessened bond proportion of the non-abrasive center are of real` practical value becauseA the supporting center may contribute by far a greater proportion of the surface to be tru'ed than does the thin diamond abrasive rim.

Below are given by Way of example compositions of vitrifled bonded diamond wheels which I have made containing silicon in the diamond f assess? derstood that all matter hcreinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and notvin a limitlnl sense.

I claim:

1. A vitrifled-bonded abrasive article comprising'the Abonded reaction product, as a result of ring. of a mix that comprises abrasive grains,

wheel of Example 4 the body material was a mixture of silicon and vitreous silica, proportioned alike both in the rim and the center so as to avoid detrimental differential expansion bel tween them.

llitried bonded diamond containing abrasive wheels 7 :c V4 a: 1%."-

Example 3 Example 4 Dlamond- Diamondcontaining Sup' containing s rim M61, porting .n D011 I :hier um thick m Vol. Vol. Vol. Vol. il Diamond. 100 grit size. 25 25 40 Silicon, ballmilledm.. 25 v lli Silicon, through 100 onto 210 mesh screen. 65 39 vitreous silica, ball milled 10 Vitreous silica, through 100 onto 210 mesh screen Bond A 35 35 3. Bond B 2) i) Potes l5 16 l5 1I Bond B consists of 35 parts of 'ball clay and 65 parts of the frit of bond A with two parts of aluminum powder and it is a weaker bond thar bond A by virtue of its greater clay content.

The wheels of Examples 3 and 4 were excellent mechanically, were strong integral structures, and g`ave excellent results in grinding cemented carbides. They are especially free-cutting as compared with metal bonded diamond grinding' wheels.

Although so far as certain features of the inn vention are concerned it is embodied ina grind- I ing wheel, nevertheless certain advantages of the invention can be obtained when it is' embodied in other types of abrasive articles such as honing sticks, abrasive stones, inserts, segments, and the like.

It will' thus .be seen that 'there has been provided by this invention an article of manufacture and a method' in which the various objects hereinabove set forth together with many thor-` oughly practical advantages are Isuccessfully s achieved. As various possible embodiments might be made of the mechanical features of the'above invention andas the art herein described might be varied' in various parts, all without departing from the scope of the invention, it is to be unmetallic granules of metallic silicon, and vitrinable bond, the metallic granules being present in the product in an amount, exclusive of any oxidation product formed during nring, to constitute substantially 15% by volume, or more, of the volume of the vitrifled-bonded article and bein! bonded by and distributed throughout the vitrified bond thereby to reinforce the bond and t0 form with the vitrifled bond a compound framework of metallic granules and vitriiied bond material, of which the metallic granules are material structural parts, said abrasive grains being distributed throughout and supported by said compound framework and bonded therein by the vitried bond of said framework.

2. A vitrifled-bonded abrasive article having a unitary body comprising a vltrifled-bonded abrasive layer anda vitrifled-bonded backing layer, and being the unitarybonded reaction product as a result of ring together the two layers, one of which comprises abrasive grains, metallic granules preponderantly of metallic silicon, and vitrifiable bond, and the 4'other of which comprises vitriflable bond and metallic granules preponderantly of metallic silicon.- vsaid metallic granules being present in the vitried abrasive layer in an amount, exclusive of any oxidation product formed durlnglilring, to constitute substantially 15% by volume, or more, of the voli vitrifled bond, and said metallic granules being present in the vitrifled-"bonded backing layer in an amount, exclusive of any oxidation product formed during firing. to constitute substantially 40% by volume, or more, of the volume of the vitrifled backing layer and being bonded by and distributed in said amount throughout the vitrifled hond of said vitrified backing layer to form a compound framework of which the said metallic granules are material structural parts thereby to constitute said backing layer to support said vitrifled-bonded abrasive layer.

3. A'vitriiled-bonded abrasive article comprising the bonded reaction product, as a result of firing, of a mix that comprises" abrasive grains, metallic granules of metalli/csilicon. and vitrinable bond, the metallic granules being present in the product in an amount. exclusive of any oxidation product formed /during ring, to constitute substantially 15% by volume, or more, of the volume ofthe vitrined-bonded article 4and being bonded by and distributed throughout the vitrified bond thereby to reinforce the bond and to form with the vitrified bond a compound framework of metallic granules and/yitried bond material, of which the metallic granules are material structural parts, said vitried bond being present in an xamount to constitute on the order of 35% by volume of the fired` article and said-- Y ing layer in an vamount of said backing layer v metallic granules of metallic abrasive grains being present in an amount to constitute on the order of'25% by volume of the fired article and being distributed throughout and supported by said compound framework and work.'

4. A vitriiied-bon'ded l A,bonded therein by the vitrifledbond of said frameabrasive article comprising the bonded reaction product, as a result of i firing. of a mix that comprises abrasive grains, vltriable bond, and body material comprising metallic granules of metallic' silicon and granules of vitreous silica, the metallic granules being present in the product in an amount, exclusive of any oxidation product formed during ring, to constitute a substantial proportion of the volume of the vitrled-bonded article and the vvitreous silica granules being present in an amount to constitutes material proportion of the volume of the vitried bonded article, both said metallic granules and said vitreous silica granules being bonded by and distributed throughout the vitriiled bond thereby to reinforce the bond and to form with the vitrifled bond a compound framework of which both said,meta'llic granules and said vitreous silica granules are material structural parts, said abrasive grains being distributed throughout and supported by said compound v therein by the vitried framework and bonded bond of said framework. f.-

5. /A vitrifled-bonded abrasive article having a unitary body comprising a vitrifled-bonded abrasive layer and a vitrifled-bonded layer and being the unitary bonded product as a result of ring together reaction g formed during firing, to constitute a substantial proportion of the volume of the vitrified abrasive layer and being bonded by and distributed throughout the vitried bond thereby to reinforce the` bond and to form with the vitriled bond a compound framework -of metallic grany ules and vitrifled bond material, of which the metallic granules are material structural parts, said abrasive grains being distributed throughthe two. layers, one of which comprises abrasive backing metallic silicon, to constitute a substantial pro-v out and supported by'said compound framework and bonded therein by the vitried bond of said framework, said granules of vitreous silica being present in the vitriied-bonded backto constitute a material proportion vof the volume thereof and being bonded by and distributed throughout the vitri- `lied bond of said backing layer to form a compound framework of-which said granules of vitreous silica are material structural parts, and

said metallic silicon being Present in an amount at least sufficientl to prevent deleterious swelling during firing.

6. A vltrified-bonded abrasivearticle having a unitary body comprising a vitried--bonded abrasive layer and a vitrifed-bonded backing layer and being the unitary bonded product as. a resultof firing together the two layers, vone of which comprises abrasive grains,

silicon, and vitrireaction y 5 ent in the vitriiied abrasive layer in an amount, exclusive of any oxidation product formed during firing, to constitute a substantial proportion of the volume of the vitrified abrasive layer and being bonded by and distributed throughout the vitried bond thereby to reinforce the bond and to form with the vitried bond a ycompound framework of metallic `granules and .vitriiied bond material, of which .the metallic granules are' material structural parts, said abrasive grains being distributed throughout and supported by said compound framework and bonded therein by the vitrified' bond of said framework, said metallic granules being present in the vitrified bonded backing layer in an amount, exclu- .sive of any oxidation product formed during ing the bonded reaction product, as a result of firing, of a mix that comprises abrasive grains,.

metallic granules `of oxidizable metallic silicon, and vitriflable bond, the metallic granules being present in the vitried product in an amount, exclusive of any oxidation product formed during firing as a result of oxidation of some of said portion of the volume of the vitried article and being bonded by, and distributed in said amount throughout, the vitrified bond thereby to reinforce the bond and to form with the vitried bond a built-up compound framework of which the metallic granules of metallic silicon, in said substantial proportion, are material structural parts, said abrasive grains ,being distributed throughout and supported by said built-up framework and bonded therein by the vitrified bond of said framework.

8. A vitried-bonded abrasive article having a `unitary body comprising a vitried bonded abrasive layer and a vitried bonded backing layer, and being the unitary bonded reaction product as a result of firing together two mixes, one of whichv comprises abrasive grains and vitriflable bond and the other of which comprises vitriflable bond and metallic granules of oxidizable metallic silicon, the metallic granules being present in the vitrified-bonded backing able bond, and the other ofA which comprises y vitriilable bond, metallic granules of metallic silicon," and body material comprising granules of vitreous silica, the metallic granules being preslayer in an amount, exclusive of any oxidation product formed Aduring firing as a result of oxidation of some of said metallic sil-icon, to constitute a substantial proportion structurally ofthe said backing layer and the `said-metallic granules being bonded by, and distributed in -said substantial proportion throughout, the vitriiledv bond of said backing layer to form a built-u p compound framework of which said metallic granules are, in said .substantial proportion, material structural parts to thereby constitute said backing layer to swport said abrasive layer.

9. AV vitriiied-bondedA abrasive article having a unitary body comprising a vitrled-bonded abrasive layer and a vitried-bonded layer, and being the unitary bonded reaction y product asa result of ring together two mixes,

fiable bond and theother of which comprises vitriiiable Abond and granules of an oxidizable metallic silicon and body material comprising granulesof vitreous silica, granules of said oxidizable metallic silicon and granules of said vitreous sil-ica being present in the vitriedbonded backing layer in an amount, exclusive of any oxidation product formed during ming as a result of oxidation of some of said metallic silicon, to constitute a substantial proportion structurally of the said backing layer and the said granules of oxidizable metallic silicon and the said granules of vitreous silica being bonded vby, and distributed in said substantial proportion throughout, the vitried bond of said backin-g layer to form a built-up framework of which said oxidizable metallic silicon granules and vitreous silica granules are in said amount material structural. parts to thereby constitute said backing layer to support said abrasive layer.

ROBERT H. LOMBARD. 

